Pacific Giant Salamander

Contents:
 
Links:
Taxon, Status, and Ranks Habitat Photos
General Description State Status Comments
Identification Tips Inventory & Research Needs Key Features
Phenology Threats & Mgmt Concerns
Range References Distribution Map

Taxon, Status, and Rank

Species Dicamptodon tenebrosus (Eschscholtz)
Family Dicamptodontidae
(Giant Salamanders)
Status None
State Rank S5
Global Rank G5

General Description

This is a large, stocky, marbled gold and brown salamander with a rounded snout, indistinct costal grooves and a laterally compressed tail. The largest terrestrial salamander in North America; adults reach lengths of 170 mm snout-vent length and 340 mm total length. The marbling becomes less distinct as the salamander ages and may only be present on the head of very old individuals. The ventral surface is usually white to light gray (may also be dark in some individuals) without other markings or pattern. Twelve to thirteen costal grooves are present but indistinct.

The eggs are laid under rocks or logs and are guarded by the females. The eggs are white without pigmentation, laid singly and attached to the nest wall by short pedicels.

Larvae are stream-type with short gills and a low tail fin that ends on the body near the hind limbs. The tips of the digits are black and hard (cornified). Small larvae (< 55 mm snout-vent length) are light brown above and white below. Subtle tan to yellowish streaks of pigmentation is present on the dorsal and lateral surfaces in indistinct streaks. The tail is mottled with darker pigmentation and there is usually a dark blotch at the tip of the tail. Larger larvae (>55 mm snout-vent length) are more mottled, have dark ventral surfaces and the mottling and spot on the tail are less conspicuous or may be absent. See Photos Page.

Identification Tips

Transformed Giant Salamanders are easily distinguished from all other Washington salamanders by the marbled pattern on head and dorsal surfaces. Transformed Cope’s Giant Salamanders are rare; almost all individuals found are larval salamanders. The traits that distinguish the two species are subtle. The Pacific Giant Salamander is larger, has a wider head and longer legs. The first two traits require experience working with giant salamanders to learn how to discern these differences. To determine relative leg length, the forelegs are gently pressed backward against the body and the hind legs forward against the body (adpressed legs). The toes will touch or cross in the Pacific Giant Salamander but will not with a Cope’s Giant Salamander.

Eggs: The female will be present in the nest chamber guarding the eggs. Nussbaum et al. (1983) provides a description of individual eggs.

Larvae: The short gills and low tail fin distinguish stream-type salamanders from pond-type. Of the stream-type larvae, the torrent salamanders (Rhyacotriton species) can be easily distinguished by their orange ventral coloration and tiny gills that are barely visible when the salamander is out of water.

Differentiating Cope’s Giant Salamander larvae from Pacific Giant Salamander larvae is challenging, especially for smaller larvae (<50 mm snout-vent length). Range differences can be used; only the Pacific Giant Salamander has been documented north of the Nisqually River in Pierce, King, Snohomish, Skagit and Whatcom counties (see Distribution maps). Species identifications based on location should be indicated in field notes or data submitted to museums or databases.

For larvae 50 mm snout-vent length or greater, the following traits can be used to determine species. The head of the Pacific Giant Salamander is wider at the base than at the snout and the head width is more than 1/5 the snout-vent length. Toes touch or overlap when legs are adpressed against the body. The tan to yellow pigmentation on the dorsal and lateral surfaces of the body is clustered in indistinct streaks as if someone painted it on the surface with a dry brush; not clustered into spots and blotches. See Key Features Page.

Phenology

Metamorphosed forms spend most of their lives in the subterranean environment and are rarely seen. Most surface activity takes place at night although diurnal activity is also reported. Larval forms are the life stage most likely to be observed. Larvae can be observed year round in flowing water bodies and may also be present in higher elevation ponds and lakes connected to flowing water bodies. Breeding takes place in the spring and fall. The female lays her eggs in the spring and then guards the eggs until they hatch about 200 days later. The larval period is 18 to 24 months or may be permanent (gilled adults) depending on local conditions. Sexual maturity takes place in all forms around 115 mm snout-vent length.

Range

In Washington, Pacific Giant Salamanders occur primarily west of the Cascade Crest in the Pacific Coast, Puget Trough and West Cascades ecoregions. They also occur east of the Cascade Crest in some areas of the East Cascades Ecoregion. They do not occur north of the Chehalis River on the Olympic Peninsula. See Distribution Map.

For information on the complete range of this species, see NatureServe Explorer.

Habitat and Habits

Pacific Giant Salamanders are primarily associated with small to medium-sized mountain streams in moist coniferous forests. They may also enter larger flowing water bodies and still water habitats connected to the streams they inhabit. Breeding sites are limited to smaller flowing water bodies. Pacific Giant Salamanders are often the dominant vertebrate within streams. Most occurrences are found below 960 m (3,150 ft) elevation but populations have been observed at higher elevations.

Metamorphosed forms are rare in comparison to the larval forms. Most surface activity is at night or during daytime wet conditions. Most individuals are found within 50 m of steams. In Oregon, observations have been made of individuals as far as 400 m from streams. They are alert and will flee underground when approached. If captured, their defensive behaviors include an audible growl, tail waving, emitting of noxious and toxic skin secretions and biting.

Larvae and gilled adults can be observed day or night in streams. During the day, they are typically concealed under rocks or woody debris. Occasionally they can be observed moving about in the stream. More typically, one must search for them by gently poking under rocks and woody debris, gently lifting cover objects and/or searching for them visually with the assistance of a glass-bottom viewing bucket or similar item placed in the water. Methods more destructive to the stream bed call for good justification. At night, they are less likely to be sheltered and can be observed moving about in the stream. To capture them, it is necessary in most cases to use a hand-held net or to place a small net across the steam channel. For small larvae, an aquarium net is sufficient. To prevent introduction or transfer of disease, care should be taken to sterilize any nets they have been used on fish and also to sterilize nets between each stream.

State Status Comments

This species is common and occurs throughout western Washington. The main concerns for this species have to do with all land uses that contribute to stream sedimentation or elevated stream temperatures.

Inventory and Research Needs

Observations that occur in areas that are not indicated on the distribution map can be submitted to the Washington Department of Fish and Wildife herp database by contacting Lori Salzer by E-mail salzeljs@dfw.wa.gov. Photo vouchers including dorsal, ventral and lateral views are preferred.

Current or Recent Research in Washington

The Cooperative Monitoring Evaluation and Research (CMER) Committee and Adaptive Management Program have funded a Type N Experimental Buffer Treatment Study that addresses the effectiveness of Forest Practice’s prescribed riparian buffers along non-fish bearing streams. Four Forests and Fish Agreement target species (Coastal Tailed Frog [Ascaphus truei] and three species of Torrent Salamanders [Rhyacotriton]) along with Cope’s and Coastal Giant Salamanders (Dicamptodon) are one focus of the study. It is a before-after control-impact designed study that compares one application of the current prescribed buffer to a shorter buffer, longer buffer, and an unharvested reference basin located on timber-managed land. The research will focus on potential changes in amphibian occupancy and abundance before and after timber harvest. The study is intended to inform the current buffer prescription rule for non-fish bearing streams in Washington State. Research is conducted by the Washington Department of Fish and Wildlife Habitat Program, the Washington Department of Ecology, Northwest Indian Fisheries Commission, and Weyerhaeuser. Study basins are located on private, state, and federally owned lands. Numerous stakeholders support this study including major and minor private landowners, state and federal agencies, tribes, and an environmental caucus.

Threats and Management Concerns

Activities that alter the integrity of small and medium-sized forested streams are of concern especially those actions that increase water temperature and sedimentation. Forestry practices that do not protect streams from sedimentation may be particularly problematic for salamander populations that occur in low-gradient streams where increased silt deposition may eliminate microhabitats crucial for the survival of the species. This happens when silt fills spaces between rocks and logs that would otherwise be used as sheltering, hiding and nesting sites.

References

Bury and Corn 1988b, Corn and Bury 1989, Nussbaum et al. (1983) and Petranka (1998).

Personal communications: Aimee Macintyre


Hallock, L.A. and McAllister, K.R. 2009. Pacific Giant Salamander. Washington Herp Atlas. http://www1.dnr.wa.gov/nhp/refdesk/herp/

Last updated: May 2009


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